1. Field of the Invention
The invention relates generally to lasers that generate visible or ultraviolet laser light. More specifically, it relates to the field of diode-pumped solid-state lasers (DPSSLs).
2. Description of Related Art
Lasers that generate visible light and ultraviolet radiation have many important uses, such as medical applications, laser light sources for projection displays, and even laser light shows. However, it has proven difficult to design and manufacture lasers that generate light over the entire visible range and into the ultraviolet, for a number of reasons. One reason is that the wavelength of laser emission is determined by the material properties of the gain medium, and therefore the available colors are restricted by these known transitions. For most uses a gain media that emits at discrete transitions, such as Nd:YAG is preferable; however a small number of strong (and therefore useful) energy transitions of the gain medium appear only at a few discrete wavelengths. For example, the strongest Nd3+ transitions are in the infrared. Outside of these discrete wavelengths, it can be difficult to obtain and sustain appropriate lasing transitions.
One conventional way of accessing wavelengths that do not lase directly is to convert the laser emission wavelength to a different wavelength, and the process of converting the laser emission to a different wavelength is called “frequency conversion.” For example, conventional frequency-converted DPSSLs generate visible laser light utilizing a nonlinear element in the laser cavity to convert the fundamental laser emission (at a “fundamental frequency”) to a higher, visible converted frequency. However, the addition of the nonlinear element increases noise and creates instabilities in the output beam, reduces efficiency, and significantly increases the cost of production. Some specific examples of prior art are discussed below.